The present invention relates to a novel process for lowering the incidence of clustering or sticking of reducible iron-containing material during the direct reduction of said material. The process comprises contacting the reducible iron-containing material with a dispersion which comprises at least one non-pozzolanic particulate material and at least one fluxing agent. Said contacting occurs at a point prior to the introduction of said reducible iron-containing material into the direct reduction furnaces. In another embodiment, the process comprises contacting the reducible iron-containing material with a dispersion which comprises an aluminum-containing clay.
It is a well known technical problem that particulate reducible iron-containing material tends to stick together, forming large clusters or agglomerates during their processing in a direct reduction furnace. These clusters tend to remain intact during treatment in a direct reduction furnace, impeding appropriate flow through the furnace. One possible though unacceptable solution to this problem is lowering the furnace temperature and through put. From the perspective of efficiency alone this solution is not appropriate.
Other solutions have been suggested to decrease clustering in a direct reduction furnace while maintaining a high processing rate through the furnace. For example, European Patent Specification No. 207 779 teaches application of a cement coating to the surface of burned iron ore prior to direct reduction in order to prevent agglomeration in the direct reduction furnace. U.S. Pat. No. 3,062,639 discloses a process for treating reducible iron oxide by contacting the iron oxide with a solution comprising an element selected from the group consisting of an alkali metal, an alkaline earth metal, a metal of group V, a metal of group VIB, boron, and silicon. This is intended to prevent clustering in the furnace reduction zone.
U.S. Pat. No. 13,549,352 discloses a process for substantially suppressing bogging (clustering) in an iron ore reduction process by adding directly to a ferrous reduction bed a dry powder selected from alkaline earth metal oxides or carbonates, especially the oxides of calcium and magnesium.
In U.S. Pat. No. 3,975,182, a method to produce iron oxide pellets which do not form clusters in a vertical shaft moving bed is disclosed. In that method, a surface coating of lime, limestone or dolomite is formed on iron oxide pellets. The lime-containing material is added in dry form in a balling machine with a spray of a little water to promote adhesion. The pellets are then fired to form a hard coating.
DE-OS-2 061 346 discloses a process for reduction of iron ore pellets which consists of coating said pellets with a ceramic powder prior to introduction into the direct reduction furnace. A special adhesive may be sprayed on the pellets in order to promote the adhesion of the ceramic powder to the pellets.
However, such above mentioned solutions are not adequate to overcome ore clustering in direct reduction furnaces at the processing rates and conditions currently required.
Accordingly, the development disclosed herein surprisingly lowers the occurrence of clustering of reducible iron-containing material and improves material flow in direct reduction furnaces.